: Tobacco smoking is the number one health problem accounting for more illness and death than any other single factor in the U.S. Nicotine, the major alkaloid in tobacco, has been shown to release dopamine (DA) from its presynaptic terminals, which is shown to be critical for its reinforcing effect leading to its abuse liability. Emphasis in the literature has been placed on the effect of nicotine on DA release, whereas the role of the dopamine transporter (DAT) has not been fully elucidated. Our preliminary data from our in vivo voltammetric studies demonstrate that following acute nicotine administration, DA clearance is increased in a dose-related manner in rat striatum and medial prefrontal cortex; however, the pattern of the dose-response curves is different in these two brain regions. The research proposed in this application is designed to test the hypothesis that nicotine regulates DAT function through an interaction with nicotinic receptor sites. The proposed specific aims are to determine the effect of repeated peripheral NIC administration on DAT function in striatum and cortex to assess differential brain region specific nicotine-induced regulation of DA using in vivo voltammetry, determine if an increase in DAT efficiency is responsible for the nicotine-induced increase in DAT function using [3H]DA uptake and [3H]GBR12935 binding assays, determine if increased trafficking of DAT from internal sites to the presynaptic terminal membrane using the biotinylation assay accounts for the increase in DA clearance in response to nicotine administration, and if this response is mediated by nicotinic receptors. Results from these experiments will provide a better understanding of the role of DAT in nicotine addiction and begin to assess the mechanism whereby nicotine alters DAT function.